small mapResult() documentation fix

[truecrunchyfrog]

replace my with by

[hamzaremmal]

Hey @truecrunchyfrog, thanks for the contribution. Can you please sign the Scala CLA (https://www.lightbend.com/contribute/cla/scala). Once done, I will restart the workflow to have a ✅ PR.

[dwijnand]

Probably best fixing upstream https://github.com/scala/scala/blob/2.13.x/src/library/scala/collection/mutable/Builder.scala, which presumably we'll merge with at some point, rather than fix it here.

[hamzaremmal]

Probably best fixing upstream https://github.com/scala/scala/blob/2.13.x/src/library/scala/collection/mutable/Builder.scala, which presumably we'll merge with at some point, rather than fix it here.

Yes, I was going to do it

[hamzaremmal]

Raised in scala/scala#10861